1. Field of the Invention
The invention relates to the field of the detection of hydrocarbons other than methane in a gas comprising or essentially comprising oxygen and in particular a gas comprising at least 95% of oxygen with impurities, in particular hydrocarbon impurities, the said hydrocarbon impurities being, for example, present at less than 200 ppm.
The invention also relates to units for the production of gases from the air. This is because the presence of nonmethane hydrocarbons in the liquid oxygen bath of the evaporators of these production units leads to a risk of explosion when certain concentration limits are exceeded. These limits are defined in the operating instructions for the production units.
2. Description of the Related Art
The techniques currently used to identify and detect these hydrocarbons are, on the one hand, chromatography and, on the other hand, infrared spectrometry (FTIR).
Chromatography is a technique which has been used for a very long time. It is sequential and only allows the detection and measurement of a few preselected hydrocarbons. The capital investment and the maintenance costs of the chromatograph are high.
Infrared spectrometry (FTIR) is a technique which, although more effective than chromatography, is not completely comprehensive, as it requires an examination of the spectrum in order to search for an impurity which would not have been preselected. In addition, the equipment requires a high capital investment.
The problem is thus posed of finding a novel method and a novel device which make possible continuous measurement and continuous detection of hydrocarbons other than methane in a gas essentially comprising oxygen.
The problem is also posed of finding a method and a device which are simpler to employ and less costly than the prior techniques and devices.
The problem is also posed of finding a method and a device which make possible continuous measurement and continuous detection of hydrocarbons other than methane in a gas essentially comprising oxygen, the said hydrocarbons other than methane being present, with respect to methane, in a proportion of the order of a few percent.
The problem is also posed of ensuring the safety of units for the production of gases from the air, comprising an evaporator, by the continuous comprehensive detection of nonmethane gaseous hydro-carbons at a concentration of a few ppm (for example: less than 5 ppm) in the oxygen of the evaporator, which can itself comprise methane, for example at approximately 50 ppm.